A wheelchair with two large diameter wheels in the back and two small diameter wheels in the front and a short wheelbase in-between the large and small wheels makes for a very good performer when indoors on smooth surfaces. The short wheelbase allows the wheelchair to be maneuvered between obstacles and the smooth surfaces allow the small front wheels to roll easily. The small front wheels also allow the wheelchair user to get closer to obstacles and not be limited by the front wheels sticking out and interfering with obstacles. These traits that make indoor use of a wheelchair good are the same traits that make for difficulties when the wheelchair is used outdoors. The short wheelbase makes the wheelchair unstable when rough ground is attempted and the same small wheels that stay out of the way and roll so nice indoors on smooth floors often get hung up on small bumps and the drag can often upset the wheelchair user and bring them to an abrupt halt and in the worst case throw the user out of their chair.
U.S. Pat. Nos. 7,735,847 and 8,152,192, both of which are incorporated by reference herein, describe an all terrain attachment, marketed as the FreeWheel® wheelchair attachment (see www.gofreewheel.com), that solves these issues for many wheelchairs by effectively lengthening the wheelbase to provide more stability and also taking the small front wheels out of the picture by raising them off the ground and replacing them with a larger diameter wheel further out front. The FreeWheel attachment can be quickly and easily installed onto an existing wheelchair thereby allowing the user to experience better performance in terms of ease of rolling over rough terrain due to less resistance, and also to feel more secure in such environments due to the longer wheelbase.
However, since the existing FreeWheel attachment was designed to couple to the footrest of a rigid-frame wheelchair, it does not work with a folding wheelchair. A rigid-frame wheelchair typically includes a solid footrest construction, and the chair can be disassembled and stored when not in use. A folding wheelchair, however, typically has a pair of folding, detachable two-piece footrests, and thus no place to attach the FreeWheel attachment. Thus, there is a need for a way to support the use of an all terrain attachment on a folding wheelchair.